Nonterrestrial cellular mobile telecommunication network

ABSTRACT

The multidimensional cellular mobile telecommunication system extends the usage of existing cellular mobile telecommunication radio frequencies allocated for ground-based communications to non-terrestrial mobile subscriber stations by adding an overlay of non-terrestrial cells of predetermined geometry and locus in space to the existing ground-based cellular cell site network. The polarization of the signals produced by the non-terrestrial antenna elements is a polarization that is different than and preferably substantially orthogonal to the polarization of the cellular radio signals produced by the ground-based antennas, such as a horizontal polarization, to thereby minimize the possibility of interference with the vertically polarized ground-based radio signals. Furthermore, the control signals exchanged between the non-terrestrial mobile subscriber stations and the non-terrestrial cell site controller are architected to avoid the possibility of interference with ground-based cell site transmitter-receiver pairs. In particular, the control channels used for the non-terrestrial mobile subscriber stations are selected such that the control signals transmitted in these channels are unrecognizable to the ground-based mobile subscriber stations and cell site transmitter-receiver pairs, so that even if broadcasts from a non-terrestrial mobile subscriber station reach a ground-based mobile subscriber station or cell site receiver, they cannot be interpreted and are rejected out of hand.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 07/847,920, filed Mar. 6,1992 and titled "MobileTelecommunications", now U.S. Pat. No. 5,557,656.

FIELD OF THE INVENTION

This invention relates to cellular communications and, in particular, toa cellular mobile telecommunication system that provides service to bothterrestrial (ground-based) and non-terrestrial mobile subscriberstations using the same cellular telecommunication channels for bothclasses of users.

PROBLEM

It is a problem in the field of cellular mobile telecommunicationservices to provide customers with high quality communication servicesvia a wireless communication medium. Existing cellular mobiletelecommunication systems serve terrestrial (termed ground-based herein)mobile subscriber stations, but this service is not presently extensibleto non-terrestrial mobile subscriber stations due to signal interferenceproblems between ground-based and non-terrestrial mobile subscriberstations. The regulatory agencies responsible for telecommunicationstherefore presently do not permit the provision of such service.

Cellular mobile telecommunication systems provide the service ofconnecting mobile telecommunication customers, each having a mobilesubscriber station, to both land-based customers who are served by thecommon carrier public telephone network as well as other mobiletelecommunication customers. In such a system, all incoming and outgoingcalls are routed through mobile telecommunication switching offices(MTSO), each of which is connected to a plurality of cell sites (basestations) which communicate with mobile subscriber stations located inthe area covered by the cell sites. The mobile subscriber stations areserved by the cell sites, each of which is located in one cell area of alarger service region. Each cell site in the service region is connectedby a group of communication links to the mobile telecommunicationswitching office. Each cell site contains a group of radio transmittersand receivers with each transmitter-receiver pair being connected to onecommunication link. Each transmitter-receiver pair operates on a pair ofradio frequencies: one frequency to transmit radio signals to the mobilesubscriber station and the other frequency to receive radio signals fromthe mobile subscriber station. The first stage of a cellularcommunication connection is set up when a transmitter-receiver pair in acell site, operating on a predetermined pair of radio frequencies, isturned on and a mobile subscriber station, located in the cell site, istuned to the same pair of radio frequencies. The second stage of thecommunication connection is between the communication link connected tothis transmitter-receiver pair and the common carrier public telephonenetwork. This second stage of the communication connection is set up inthe mobile telecommunication switching office, which is connected to thecommon carrier public telephone network by incoming and outgoing trunks.The mobile telecommunication switching office contains a switchingnetwork to switch mobile customer voice and/or data signals from thecommunication link to an incoming or outgoing trunk. The mobiletelecommunication system is controlled by a mobile telecommunicationcontroller at the mobile telecommunication switching office and a cellsite controller at each cell site associated with the mobiletelecommunication switching office. A plurality of data links connectthe mobile telecommunication controller and the associated cell sitecontrollers. The mobile telecommunication controller operates undercontrol of complex software and controls the switching network. Themobile telecommunication controller also controls the actions of theassociated cell site controllers by generating and interpreting thecontrol messages that are exchanged with the associated cell sitecontrollers over the data links. The cell site controllers at each cellsite, in response to control messages from the mobile telecommunicationcontroller, control the transmitter-receiver pairs at the cell site. Thecontrol processes at each cell site also control the tuning of themobile subscriber stations to the selected radio frequencies.

Each cell in the ground-based cellular mobile telecommunication networkcomprises a predetermined volume of space radially arranged around thecell site transmitting antenna with the region of space roughlyapproximating a cylindrical volume having limited height. Since, all ofthe mobile subscriber stations are installed in ground-based units (suchas motor vehicles) in traditional cellular mobile telecommunicationsystems, the antenna radiation pattern of the cell site is aligned to beproximate to the ground and the polarization of the signals produced bythe cell site antenna is vertical in nature. In order to prevent theradio signals in one cell site from interfering with radio signals in anadjacent cell site, the transmitter frequencies for adjacent cell sitesare selected to be different so that there is sufficient frequencyseparation between adjacent transmitter frequencies to avoid overlappingtransmissions among adjacent cell sites. In order to reuse the samefrequencies, the cellular telecommunication industry has developed asmall but finite number of transmitter frequencies and a cell siteallocation pattern that ensures that two adjacent cell sites do notoperate on the same frequency. When a ground-based mobile subscriberstation initiates a call connection, control signals from the local cellsite transmitter cause the frequency agile transponder in theground-based mobile subscriber station to operate at the frequency ofoperation designated for that particular cell site. As the ground-basedmobile subscriber station moves from one cell site to another, the callconnection is handed off to the successive cell sites and the frequencyagile transponder in the ground-based mobile subscriber station adjustsits frequency of operation to correspond to the frequency of operationof the transmitter located in the cell site in which the ground-basedmobile subscriber station is presently operational.

This existing cellular mobile telecommunication system is presently inwidespread use and has been designed to eliminate the problem offrequency overlap among adjacent cell sites and to minimize the numberof frequencies required to serve vast areas without encountering thepossibility of frequency overlap. These existing cellular mobiletelecommunication systems, however, are inoperable when the user'smobile subscriber station is non-terrestrial in nature. In particular,the provision of cellular mobile telecommunication services to aircraftis inconsistent with the architecture of the existing ground-basedcellular mobile telecommunication network since the antenna pattern ofthe existing ground-based cellular mobile telecommunication systembroadcasts a signal in a pattern proximate to the ground and the patternof frequency allocation for the pattern of cell sites is not extensibleto aircraft. In particular, an antenna pattern that would be capable ofserving a fast moving aircraft would have to cover a sufficient volumeof space to minimize the number of station hand offs as the aircrafttraverses one cell site after another. For the non-terrestrial mobilesubscriber station to have an adequate sized cell site, that cell sitewould span a large number of the existing ground-based cell sites.Therefore, the existing pattern of frequency reuse would be disruptedand there presently is no frequency allocated or available forallocation to such purpose. If additional frequencies were allocated fornon-terrestrial cellular telecommunication systems, all existingcellular telecommunication equipment would have to be redesigned to becapable of operating at these new frequencies and yet remain compatiblewith the existing pattern of cellular telecommunication services.

Thus, the existing cellular mobile telecommunication network isincapable of being simply extensible to provide service tonon-terrestrial mobile subscriber stations and the architecture ofchoice installed in all ground-based cellular mobile telecommunicationsystems is fundamentally inoperable as it stands for use withnon-terrestrial mobile subscriber stations. Therefore, the existingcellular mobile communication network is by its very nature simply a twodimensional ground-based system with the inability to be extensiblebeyond that limited definition. With this limitation, cellular mobiletelecommunication services are completely unavailable for aircraft andaircraft must use a separate communication system that operatesindependent of the existing cellular mobile telecommunication networkand which requires its own pattern of transceiver antennas, unique radioequipment and control software.

SOLUTION

The above described problems are solved and a technical advance achievedin the field by the multidimensional cellular mobile telecommunicationsystem of the present invention. The multidimensional cellular mobiletelecommunication system extends the usage of existing cellular mobiletelecommunication frequencies allocated for ground-based cellularcommunications to non-terrestrial mobile subscriber stations in a mannerthat avoids the possibility of signal interference between theground-based and non-terrestrial mobile subscriber stations. Inparticular, the multidimensional cellular mobile telecommunicationsystem expands the two-dimensional adjacent cell configuration of thepresent day ground-based cellular telecommunication network by theaddition of an overlay of non-terrestrial cells (coverage areas) ofpredetermined volume, each of which non-terrestrial cells can overlapnumerous ground-based cells and which non-terrestrial cells arethree-dimensional in nature. Each non-terrestrial cell in this overlaypattern is of predetermined geometry and locus in space and ispreferably adjacent to other non-terrestrial cells so that a pluralityof the adjacent non-terrestrial cells completely occupies a large volumeof space in the region immediately adjacent to and overlying theexisting ground-based cell network. In this manner, the overlay ofnon-terrestrial cells merges with the existing ground-based cells toform a seamless multidimensional cellular telecommunication network.There are a number of implementation features of this system which arecooperatively operative to enable the non-terrestrial cells andnon-terrestrial mobile subscriber stations to operate in conjunctionwith the ground-based cells and ground-based mobile subscriber stationsto provide superior communication performance. These features allfunction to reduce the possibility of interference between thenon-terrestrial and ground-based elements in the resultantmultidimensional network and the combination of these features which areused to implement a system is a function of the communication/controltechnology used for radio communication, the topography of the terrain,the communication traffic, the implementation cost of the system, andthe like. Thus, a multidimensional cellular mobile telecommunicationsystem can be implemented using only a subset of the implementationfeatures described in the preferred embodiment of the present invention.

The existing mobile telecommunication switching office is partitionablevia software to divide the physical area covered by the cells into twoor more segments, one segment of which can optionally occupy the samevolume of space as another segment. The multidimensional cellulartelecommunication network of the present invention takes advantage ofthe partition capability of these systems to create a virtual cellularnetwork which coexists with the existing cellular network and canintegrate: multiple existing ground based cellular systems, differentequipment, different vendors, different radio frequencies, can even bedifferent technologies (digital/analog; TDMA/CDMA; AMPS/narrow bandAMPS; FM/AM/PSK). The multidimensional cellular telecommunicationnetwork is seamless and overlaid on the existing ground-based cellulartelecommunication network. In this system, the existing ground-basedcell site transmitter/receiver antenna installations can be used for thenon-terrestrial mobile subscriber stations by the addition of antennaelements and the creation of an antenna pattern which is insensitive tothe reception of ground-originating or ground reflected signals andwhich antenna pattern is transmissive only in a skyward direction. Inaddition, the polarization of the signals produced by thenon-terrestrial antenna elements is a polarization that is differentthan and preferably substantially orthogonal to the polarization of theground-based cellular radio signals, such as a horizontal polarization,to thereby minimize the possibility of interference with the verticallypolarized ground-based cellular radio signals. Furthermore, the controlsignals exchanged between the non-terrestrial mobile subscriber stationsand the non-terrestrial cell site controller are architected to avoidthe possibility of interference with ground-based cell sitetransmitter-receiver pairs. In particular, the control channels used forthe non-terrestrial mobile subscriber stations are selected such thatthe control signals transmitted in these channels are unrecognizable tothe ground-based mobile subscriber stations and ground-based cell sitetransmitter-receiver pairs so that even if broadcasts from anon-terrestrial mobile subscriber station reach a ground-based mobilesubscriber station or cell site transmitter-receiver pair they cannot beinterpreted and are rejected out of hand. Optionally, thenon-terrestrial system can switch uplink and downlink frequencies to bethe opposite of ground-based mobile subscriber station pattern. In thismanner, non-terrestrial cells can be created in the region of spaceadjacent to and overlying the existing ground-based cells and theexisting cellular communication frequencies allocated for ground-basedcellular telecommunications can be reused for non-terrestrial cellulartelecommunications without the possibility of interaction between theexisting ground-based cellular mobile telecommunication system and thenon-terrestrial mobile subscriber stations. Furthermore, the transmitand receive frequencies for non-terrestrial communications can be offsetfrom the ground-based frequencies. The non-terrestrial cells can bemanaged in a manner that is analogous to, yet separate from, themanagement of the ground-based cells so that hand offs from onenon-terrestrial cell to another are managed independent of, but in acontrol manner similar to that used for the ground-based cells.

Thus, by reusing the presently allocated cellular radio frequencies andthe control philosophies of the present day ground-based cellular mobiletelecommunication systems, redesign of the existing equipment isminimized and the necessity for new apparatus is reduced to a minimum.To the mobile telecommunication switching office, the non-terrestrialcells all operate in harmony with the existing cell sites with nodiscernible differentiation among cells or stations, be theyground-based or non-terrestrial in nature. In this manner, the existingtwo dimension mobile cellular telecommunication network is extensible byuse of these novel methods and apparatus to create a multidimensionalcellular mobile telecommunication system which makes use of thepresently allocated cellular radio frequencies and presently providedservices.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 illustrates a typical prior art ground-based cellular mobiletelecommunication system that includes a plurality of mobile telephoneswitching offices;

FIG. 2 illustrates in block diagram view, the overall architecture ofthe multidimensional cellular telecommunication network of the presentinvention;

FIGS. 3-5 illustrate perspective views of a multi-cell non-terrestrialcellular mobile telecommunication system as well as the relativegeographical extent of the ground-based cells and typicalnon-terrestrial cells;

FIG. 6 illustrates a diagram of a typical non-terrestrial cell frequencyreuse pattern;

FIG. 7 illustrates a sectored non-terrestrial cell with a substantiallycylindrical antenna pattern configuration;

FIG. 8 illustrates a sectored non-terrestrial cell with a substantiallytoroidal antenna pattern configuration which includes a cylindricalantenna pattern configuration nested within the aperture of the toroid;

FIG. 9 illustrates a typical antenna mounting arrangement;

FIG. 10 illustrates the frequency allocation for a typical cell; and

FIG. 11 illustrates the signal paths that are found in the multipathinterference situation.

DETAILED DESCRIPTION

The multidimensional cellular mobile telecommunication system of thepresent invention extends the usage of existing cellular mobiletelecommunication radio frequencies allocated for ground-basedcommunications to non-terrestrial mobile subscriber stations in a mannerthat avoids the possibility of signal interference between theground-based and non-terrestrial mobile subscriber stations. Inparticular, the multidimensional cellular mobile telecommunicationsystem adds an overlay of non-terrestrial cells of predeterminedgeometry and locus in space to the existing ground-based cellular mobiletelecommunication network. The polarization of the cellular radiosignals produced by the non-terrestrial antenna elements is apolarization that is different than and preferably substantiallyorthogonal to the polarization of the cellular radio signals produced bythe ground-based antennas, such as a horizontal polarization, to therebyminimize the possibility of interference with the nominally verticallypolarized ground-based cellular radio signals. Furthermore, the controlsignals exchanged between the non-terrestrial mobile subscriber stationsand the non-terrestrial cell site controller are architected to avoidthe possibility of interference with ground-based cell sitetransmitter-receiver pairs. In particular, the control channels used forthe non-terrestrial mobile subscriber stations are selected such thatthe control signals transmitted in these channels are unrecognizable tothe ground-based mobile subscriber stations and cell sitetransmitter-receiver pairs, so that even if broadcasts from anon-terrestrial mobile subscriber station reach a ground-based mobilesubscriber station or cell site receiver, they cannot be interpreted andare rejected out of hand.

Architecture of a Cellular Mobile Telecommunication System

FIG. 1 illustrates a typical prior art ground-based cellular mobiletelecommunication system which includes a plurality of mobile telephoneswitching offices (MTSO) 102, 103, each of which is connected viacommunication facilities 1121-1124, 1131-1133 to a plurality of cellsite transmitter-receiver pairs 121-124, 131-133 (also termed basestations herein). The terms "cell site" and "cell" are sometimes looselyused in the literature, and the term "cell site" generally denotes thelocus at which the transmitter and receiver apparatus is located, whilethe term "cell" generally denotes the region of space which is served bya particular transmitter-receiver pair which is installed at a cellsite. The particular technology used to implement the communicationsbetween subscriber stations and the transmitter-receiver pairs as wellas the nature of the data transferred therebetween, be it voice, video,telemetry, computer data, and the like, are not limitations to thesystem which is described herein, since a novel system concept isdisclosed, not a specific technologically limited implementation of anexisting system concept. Therefore, the term "cellular" as it is usedherein denotes a communication system which operates on the basis ofdividing space into a plurality of volumetric sections or cells, andmanaging communications between subscriber stations located in the cellsand the associated transmitter-receiver pairs located at the cell sitefor each of these cells.

For the purpose of illustration, two mobile subscriber stations A, B areshown in FIG. 1 and are located within cells 106, 107, respectively. Aplurality of the cells 106 are interconnected with a designated mobiletelecommunication switching office 102, which serves to interconnect thetransmitter-receiver pairs 121-124 in the various cells 106 served bythe mobile telecommunication switching office 102 with the publicswitched telephone network (PSTN) to access other mobiletelecommunication switching offices as well as conventional telephoneapparatus. The cellular mobile telecommunication system also includes aroamer verification system 101 which is interconnected with the mobiletelecommunication switching offices 102, 103 via data links 104, 105,respectively. The roamer verification system 101 functions toauthenticate the identity of the mobile subscriber stations A, B andauthorize the provision of cellular telecommunication services to thesesubscribers.

The range of a particular cellular service is determined by thegeographic location of the cells. In addition, cellular mobiletelecommunication systems are not connected on a nationwide basis.Rather, the industry consists of many distinct geographical regions thatserve a specific (home) base of subscribers. For example, in FIG. 1, thebold line C--C denotes a boundary between two cellular regions, withmobile telecommunication switching office 102 being located in a firstof these regions and mobile telecommunication switching office 103 beinglocated in a second adjacent region. When cellular subscribers leavetheir home geographical region, they become "roamers." When a roamingsubscriber places a cellular telephone call from their mobile subscriberstation, the mobile telephone switching office that provides service hasno way of determining if this roamer is a valid subscriber or not, sincethis information is located in the roamer's home system. Obtaining theinformation from the home switch, and notifying the foreign mobiletelecommunication switching office of the roamer's status is the purposeof the roamer verification system, illustrated in FIG. 1.

The cellular radio telecommunication service provided in North America,for example, is designed primarily for motor vehicles and otherground-based mobile subscriber stations. The system presently in useuses a plurality of radio frequency channels in the Ultra-High Frequency(UHF) band. A channel in this system comprises a pair of UHF frequenciesin the designated band. One frequency in the channel is termed the"forward" carrier and is used for transmissions from the base station tothe mobile subscriber station, while the other frequency in the pair istermed the "reverse" carrier and is used for transmissions from themobile subscriber station to the base station. Present technologies inuse include analog Frequency Modulation (FM) as the method fortransmitting the signal with a 30 kHz frequency channel spacing. Thereis also digital transmission capability in some systems, wherein aplurality of signals are multiplexed on to the same carrier, with the 30kHz spacing between adjacent bands. A total of 832 such channels areavailable for cellular telephone use, and these channels are locatedbetween the frequencies of 824 MHz to 849 MHz, and 869 MHz to 894 MHz.The transmitter has 832 communication channels, 790 voice/datacommunication and 42 control channels. This set of channels is dividedinto two subsets, each consisting of 21 control channels and anassociated 395 voice/data channels. A first set of channels is typicallytermed the "A" side of the band and the remaining set of channels istypically termed the "B" side of the band. The 416 radio channels ineach set of channels are divided into 21 control channels and 395voice/data communication channels. The 395 voice/data communicationchannels are subdivided into seven groups of approximately 56 channelswhen used with a seven cell channel reuse plan, termed a K=7 plan.

Multidimensional Cellular System Control Channels

In this existing regulated communication environment, a particularproblem is encountered when attempting to use cellular mobile telephoneequipment from a non-terrestrial location, such as an aircraft. Theelevated position of the mobile cellular telephone station when locatedaboard an aircraft causes the signal to be broadcast over a wide area ofthe surface of the earth, where it is received by many ground-based cellsite transmitter-receiver pairs. In addition, the signal strength at aplurality of these ground-based cell site transmitter-receiver pairs maybe substantially equal, making determination of the controlling basestation a difficult choice. Thus, mobile cellular subscriber stationsare prohibited from transmitting from aircraft. The cellular telephonenetwork requires a minimum signal-to-noise ratio to enable thecommunications to be of an acceptable quality. The presently requiredseparation between signal power level and the background or noise powerlevel is typically approximately 6 dB for the non-terrestrial subscriberstation and 18 dB for the cell-site receiver for interference freecommunications. Thus, the non-terrestrial cellular communication portionof the multidimensional system must provide adequate signal strength bythe appropriate selection and siting of antenna elements within theconstraints of available signal power. In addition, the interferencebetween ground-based and non-terrestrial mobile subscriber stations mustbe obviated by the signal characteristics as well as communicationcontrol philosophy.

The communication control philosophy portion of this unique solutioncomprises a manipulation of the control channels such that controlsignals originated by a non-terrestrial mobile subscriber station cannotcause either a ground-based cell site receiver or ground-based mobilesubscriber station receiver to receive and interpret these controlsignals. The reception of signals in the allocated frequency spectrum isbeyond the practical control of the system, so the designation ofcontrol channels within the plurality of available channels representsthe method of bifurcating the volume of space into two disjunct regions:ground-based and non-terrestrial. As shown in FIG. 10, the controlchannels dedicated for use by the non-terrestrial mobile subscriberstations are those which are designated as voice/data communicationchannels for the ground-based mobile subscriber stations. Thus, eachground-based cell site transceiver communicates with the ground-basedmobile subscriber stations extant in its cell on predetermined controlchannels, which control channels are ignored by non-terrestrial mobilesubscriber stations, since these channels are voice/data communicationchannels in the view of the non-terrestrial mobile subscriber stations.Similarly, each non-terrestrial cell site transmitter-receiver paircommunicates with the non-terrestrial mobile subscriber stations extantin its cell on predetermined control channels, which control channelsare ignored by ground-based mobile subscriber stations, since thesechannels are voice/data communication channels in the view of theground-based mobile subscriber stations. Thus, the allocation of controlchannels in the non-terrestrial cells represents a paradigm shift withrespect to the adjacent ground-based cells. This philosophy can beimplemented in a cost effective manner, since the large installed baseof ground-based mobile subscriber stations and ground-based cell sitetransmitter-receiver pairs inherently reject control signals transmittedin the voice/data communication channels. It is only the newlyconstructed non-terrestrial mobile subscriber stations and theirassociated cell site transmitter-receiver pairs which must be modifiedto reassign control channels. This implementation incurs a relativelysmall cost.

An alternative implementation of the communication control philosophycomprises allocating a subset of the available channels exclusively tonon-terrestrial cellular communications, with this subset of dedicatedchannels being divided into control channels and communication channelsas with the existing channel allocation pattern. However, the dedicationof even a small number of channels can be problematic, since thesechannels are removed from all ground-based cells and can havesignificant impact on traffic handling capacity. In addition, such asolution requires the modification of all existing equipment.

Frequency Reuse Pattern

Mobile cellular telecommunication systems provide a plurality ofconcurrently active communications in the same service area, with thenumber of concurrently active communication connections exceeding thenumber of available radio channels. This is accomplished by reusing thechannels via the provision of multiple base stations in the service areathat is served by a single mobile telecommunication switching office.The overall service area of a mobile telecommunication switching officeis divided into a plurality of "cells", each of which includes a basestation and associated radio transmission tower, as shown in FIG. 1. Theradius of the cell is basically the distance from the base station towerto the furthest locus at which good reception between the mobilesubscriber station and the base station can be effected. The entireservice area of a mobile telecommunication switching office is thereforecovered by a plurality of adjacent cells. There is an industry standardcell pattern in which typically seven sets of channels are reused.Within a particular cell, the surrounding six cells are grouped in acircle around the first cell and the channels used in these six cellsdiffer from the channels used in the particular cell and from each ofthe other six surrounding cells. Thus, the signals emanating from theradio transmission tower in the particular cell do not interfere withthe signals emanating from the radio transmission towers located in eachof the six surrounding cells because they are at different frequencies.In addition, the next closest cell using the transmission frequency ofthe particular cell is far enough away from this cell that there is asignificant disparity in signal power and therefore sufficient signalrejection at the receivers to ensure that there is no signalinterference. The shape of the cell is determined by the surroundingterrain and is typically not circular, but skewed by irregularities inthe terrain, the effect of buildings and vegetation and other signalattenuators present in the cell area. Thus, the cell pattern of FIG. 1is simply conceptual in nature and does not reflect the actual physicalextent on the various cells, since the implemented cells are nothexagonal in configuration and do not have precisely delimited boundaryedges.

The control channels that are available in this system are used to setupthe communication connections between the mobile subscriber stations andthe base station. When a call is initiated, the control channel is usedto communicate between the mobile subscriber station involved in thecall and the local serving base station. The control messages locate andidentify the mobile subscriber station, determine the dialed number, andidentify an available voice/data communication channel consisting of apair of radio frequencies which is selected by the base station for thecommunication connection. The radio unit in the mobile subscriberstation retunes the transmitter-receiver equipment contained therein touse these designated radio frequencies. Once the communicationconnection is established, the control messages are typicallytransmitted to adjust transmitter power and/or to change thetransmission frequency when required to handoff this mobile subscriberstation to an adjacent cell, when the subscriber moves from the presentcell to one of the adjoining cells. The transmitter power of the mobilesubscriber station is regulated since the magnitude of the signalreceived at the base station is a function of the transmitter power andthe distance from the base station. Therefore, by scaling thetransmitter power to correspond to the distance from the base station,the received signal magnitude can be maintained within a predeterminedrange of values to ensure accurate signal reception without interferingwith other transmissions in the cell.

When a mobile unit approaches the boundary of a cell, the radio signalreceived at the base station is at a minimum level. Since the mobileunit is at the boundary of two cells, the signal power from thetransmitter located in the adjacent cell is equal to or greater than theoriginal cell and a handoff procedure is initiated. First, the cell basestation initiates a mobile unit location process in the six adjoiningcells. This is accomplished either by activation or continuous operationof a locating receiver in each of the six adjoining cells which tunes tothe radio frequency and channel on which the mobile subscriber stationis transmitting. The measured signal strength of this signal, asreceived at each of the six adjoining cells, is compared and thestrongest signal is indicative of the cell which is to receive thehandoff. If there is an available voice channel in that cell, the mobilesubscriber station is sent a message on the control channel to re-tuneits transmitter to the identified available voice channel at thetransmitter frequency of the selected cell. Simultaneously, the voiceconnection is switched at the base stations from one cell to the nextvia the Mobile Telecommunication Switching Office to provideuninterrupted service.

Multidimensional Cellular Mobile Telecommunication Network

The multidimensional cellular mobile telecommunication network of thepresent invention is illustrated in block diagram form in FIG. 2. Thisdiagram illustrates the basic concepts of the multidimensional cellularmobile telecommunication network and, for the purpose of simplicity ofillustration, does not comprise all of the elements found in a typicalnetwork. The fundamental elements disclosed in FIG. 2 provide a teachingof the interrelationship of the various elements which are used toimplement a multidimensional cellular mobile telecommunication network.

The basic ground-based cellular telecommunication network of the priorart is incorporated into this system to enable the non-terrestrialmobile subscriber stations to be integrated into the existing servicestructure. In particular, the mobile telecommunication switching office200 serves to interconnect a plurality of ground-based cells 201, 202,203 with the public switched telephone network (PSTN), as noted above.The ground-based cells 201, 202, 203 each include a transmitter-receiverpair 201TR, 202TR, 203TR and an antenna complex, which typicallycomprises a tower M1, M2, M3 to which is affixed one or more antennaelements A1, A2, A3, respectively.

Existing cellular mobile telecommunication systems use both directionaland non-directional antenna elements to implement the desired antennacharacteristic pattern. Directional antenna, as the term is used herein,does not imply that a signal is transmitted or received from aparticular direction, but that the antenna has a non-isotropic radiationpattern. A directional antenna, or a plurality of directional antennaelements, is preferably used on the ground-based cellular base stationto increase signal separation. The antenna structure used inground-based mobile cellular telecommunications is such that signalsemanating from the cell site transmitter antenna elements of antennasA1, A2, A3, propagate in a substantially radial direction from theantenna in all directions with the top of the antenna pattern beingsubstantially coplanar with the Earth's surface and at a level thatcorresponds to the elevation of the transmitter antenna above theEarth's surface. The receiver antenna has characteristics that areanalogous to that of the transmitter antenna. The polarization of thesesignals is horizontal in nature, shown by arrow GP in FIG. 2.

The mobile telecommunication switching office MTSO is partitionable viasoftware to divide the physical area covered by the cells into two ormore segments, one of which segments can optionally overly anothersegment. Typically, in ground-based cellular telecommunication systems,the available channels are divided between two competing cellularcarriers so that the service area is served by the two carriers.However, this partition ability enables the multidimensional mobilecellular telecommunication network to create a virtual cell network ofnon-terrestrial cells which coexists with the existing ground-basedmobile cellular telecommunication network. This virtual cell networkworks with multiple existing ground-based mobile cellulartelecommunication systems, different equipment, different vendors,different frequencies, can even be different technologies:digital/analog or TDMA/CDMA or FM/AM/PSK. The multidimensional mobilecellular telecommunication network is seamless and overlaid on existingground-based cellular telecommunication network.

The multidimensional cellular mobile telecommunication network adds tothe existing mobile cellular telecommunication network one or morenon-terrestrial cells. A non-terrestrial cell is defined as aninstallation which is equipped with at least one non-terrestrial cellsite transmitter-receiver pair, such as 201A and an associated antennaAA1 for receiving and transmitting cellular telecommunicationtransmissions to and from non-terrestrial mobile subscriber stations,such as aircraft 21, 22, which are equipped with mobile subscriberstation apparatus 21B, 22B. The non-terrestrial transmitter-receiverpair 201A is interconnected to the public switched telephone networkPSTN via the mobile telecommunication switching office MTSO. Thenon-terrestrial cell site antenna AA1 has a radio signal radiationpattern which is directed above a horizontal plane encompassing theantenna. The majority of the radiated radio signal is directed at anglesabove the horizontal plane, which angles are typically greater than 4°in magnitude to avoid interference with ground-based mobile cellulartelephone stations 23, 24, 25. In addition, the polarization of theseradio signals is selected to be substantially orthogonal to thepolarization of the radio signals emanating from the ground-basedantennas, and is typically vertically polarized, as shown by arrow AP inFIG. 2.

The non-terrestrial cell site transmitter-receiver pair 201A can beintegrated with an existing ground-based cell site transmitter-receiverpair, in that there is some sharing of equipment which mounts theantenna elements on a common tower M1 and/or interconnects both cellsite transmitter-receiver pairs to the public switched telephone networkPSTN. In the embodiment of FIG. 2, the non-terrestrial cell site antennaelements AA1 are mounted on the same tower M1 as the antenna elements A1used to implement the ground-based cell site.

Multidimensional Cellular System Implementation Issues

In a multidimensional cellular mobile telecommunication system, aproblem with the architecture illustrated in FIG. 2 is that thefrequencies allocated for cellular mobile telecommunications forground-based mobile subscriber stations are the same as those allocatedfor non-terrestrial mobile subscriber stations. The selection ofbroadcast frequencies for the plurality of ground-based cells is orderedto ensure that there is never an occurrence of adjacent cellsbroadcasting on the same frequency. There is an industry standardpattern of frequency allocation for cells and this industry standardpattern does not encompass non-terrestrial cells. A complicating factoris that a non-terrestrial cell has an extent significantly greater thana ground-based cell. In particular, the ground-based cells make use ofantennas mounted on a tower which is located at a site which providestypically the greatest elevation in the cell so that the broadcastpattern of the antenna covers the greatest possible area. Given that theground-based cell site transmitter is broadcasting toward the groundfrom its physical location, the extent of the cell is limited by theelevation of the antenna and any intervening physical signal obscuringfeatures in the cell, such as buildings, mountains or the like. Thislimitation is not present for non-terrestrial antennas which broadcastin a skyward direction and do not have a limited broadcast range interms of intervening features. FIGS. 3-5 illustrate a perspective view(not to scale) of the relative geographical extent of the ground-basedcells and three typical non-terrestrial cells A-C. The non-terrestrialcell site antenna pattern is typically substantially parabolic in shapeand covers a line of sight range from the siting of the antenna to thephysical horizon. Therefore, the antenna pattern for the non-terrestrialcell covers a significantly greater area than a typical ground-basedcell. Thus, a non-terrestrial cell typically covers tens or evenhundreds of ground-based cells and is adjacent to ground-based cellsthat broadcast at every one of the presently allocated frequencies forcellular mobile telecommunications. Thus, by the very nature of thisoverlap, the non-terrestrial cell has a broadcast frequency whichmatches that of at least one of the juxtaposed ground-based cells.Furthermore, the frequency reuse pattern for non-terrestrial cells mustbe such that adjacent non-terrestrial cells do not use the samebroadcast frequency. FIG. 6 illustrates a typical frequency reusepattern for non-terrestrial cells. The extent of each non-terrestrialcell enables the frequency reuse pattern to be simpler than that usedfor ground-based cells. Since the frequency reuse pattern requires onlya small subset of the presently allocated frequencies, the reuse patterncan be used to create a cell within a cell. The traffic handlingcapacity of a particular non-terrestrial cell can therefore be doubledby simply allocating twice the frequencies for this cell, creating twocells having substantially the same physical extent. Thus, there is fargreater flexibility in the non-terrestrial cells than in thecorresponding ground-based cells in terms of cell implementation andmanagement as is evidenced in additional detail by the followingdescription of the system.

In order for the non-terrestrial cells to make use of the frequenciesthat are allocated for the ground-based mobile telecommunication cells,there must be some method of ensuring that the signals broadcast to andfrom the non-terrestrial mobile subscriber stations do not interferewith the existing communications in the ground-based cells and theirground-based mobile subscriber stations. To eliminate interferencebetween non-terrestrial communications and ground-based communicationsfor mobile cellular customers, the transmit and receive antenna patternsare architected to reduce the overlap in their area of coverage, asnoted above. In addition, the polarization of the non-terrestrialtransmissions are selected to be substantially orthogonal to thepolarization of the ground-based transmissions. Alternatively, thenon-terrestrial cellular telecommunication system can switch the uplinkand downlink frequencies to be the opposite of the ground-based mobilesubscriber station pattern. The presently used forward link can be usedas the reverse link and the presently used reverse link can be used asthe forward link in the non-terrestrial mobile subscriber stationapplication. The transmitter power for the non-terrestrial mobilesubscriber stations is significantly reduced over that used byground-based mobile subscriber stations. A final element of theimplementation that prevents communication overlap is the use ofdedicated control channels for the non-terrestrial communications, whichcontrol channels are not recognized by the ground-based communications.These factors individually and in various combinations enable thenon-terrestrial communications to operate on frequencies that are usedfor ground-based communications where the non-terrestrial cells overlapthe ground-based cells using the same transmit and receive frequencies.Other design factors of the same genre are possible and can includeshifting the transmit and receive frequencies to be located between theexisting predefined frequencies, and the like.

In operation, the multidimensional cellular mobile telecommunicationsystem can comprise a separate non-terrestrial cellular mobiletelecommunication system which can be integrated with the existingground-based cellular mobile telecommunication system via a well definedinterface. FIGS. 3-5 illustrate the operation of the multidimensionalcellular mobile telecommunication system in a typical call processingsituation. In FIG. 3, the non-terrestrial mobile subscriber stationcomprises an aircraft AC which is located in non-terrestrial cell A,which non-terrestrial cell overlays a plurality of ground-based cellsGBCA. Two additional non-terrestrial cells B, C are also shown, each ofwhich overlays another plurality of ground-based cells GBCB, GBCC,respectively. The three non-terrestrial cells A-C are shown as beingoriented adjacent to each other, with cell B being between cells A andC. It is typical that other non-terrestrial cells would be implementedadjacent to cells A-C to provide complete coverage of thenon-terrestrial space that extends above the ground shown in FIGS. 3-5.For simplicity of description, only three non-terrestrial cells A-C areshown in these figures. The existing ground-based cells are eachconnected via trunks LKA-LKC to an associated mobile telecommunicationswitching office MT1, MT2, which are themselves connected together viatrunk T and to public switched telephone network PSTN via trunks PT. Inthis environment, it is typical that two different providers are servingthe network, with a first company serving region C1 and a second companyserving region C2, with the dividing line between the two service areasbeing shown in the figures by the dashed line B--B'. In this systemenvironment, a call is established from a subscriber located in theaircraft AC, using a mobile subscriber station apparatus located in theaircraft AC in the well known manner of the existing ground-basedcellular systems. The control signals from the mobile subscriber stationapparatus located in the aircraft AC are transmitted to the cell sitetransmitter-receiver pair of non-terrestrial cell A, which is served bythe first cellular company which provides service in region C1. The callis connected via trunk LKA to the mobile telecommunication switchingoffice MT1, which interconnects the call connection to the publicswitched telephone network PSTN via trunk PT, in well known fashion. Thecall connection is then extended to the designated subscriber (notshown) which is assumed for this description to be located at a "landline" station. The allocation of frequencies and the subscriberidentification for aircraft AC is managed via the non-terrestrial cellsite control software which operates independent of the ground-basedcellular network and which can be operational in the mobiletelecommunication switching office MT1 which serves the non-terrestrialcell site for non-terrestrial cell A.

The diagram of FIG. 4 illustrates the instance of the aircraft ACtraversing the boundary of non-terrestrial cell A into the extent ofnon-terrestrial cell B. Since non-terrestrial cell B is also supportedby the first provider in service region C1, the handoff between adjacentnon-terrestrial cells can be accomplished in the traditional manner,with the non-terrestrial cells surrounding the non-terrestrial cell inwhich the non-terrestrial subscriber station (aircraft AC) is presentlyactive (non-terrestrial cell A) signal the aircraft AC to ascertainwhich non-terrestrial cell provides the signal of greatest magnitude,and is therefore the candidate for handoff. The call connection isidentified as a non-terrestrial call and is therefore managed by mobiletelecommunication switching office MT1 as disjunct from the ground-basedcalls and the handoff to non-terrestrial cell B is processed in wellknown fashion with the mobile telecommunication switching office MT1managing the non-terrestrial cells surrounding cell A as a virtualnetwork, which is disjunct from the ground-based mobile cellulartelecommunication network of GBCA and GBCB. Thus, the call connection tothe aircraft AC via link LKA is transferred to link LKB as the frequencypair for communication with the aircraft AC is simultaneously switchedto match that of the new cell, non-terrestrial cell B.

The diagram of FIG. 5 illustrates the instance of the aircraft ACtraversing the boundary of non-terrestrial cell B into the extent ofnon-terrestrial cell C. Since non-terrestrial cell C is not supported bythe first provider in service region C1, the handoff between adjacentnon-terrestrial cells is still accomplished in the traditional manner,with the non-terrestrial cells surrounding the non-terrestrial cell inwhich the non-terrestrial subscriber station (aircraft AC) is presentlyactive (non-terrestrial cell B) signal the aircraft AC to ascertainwhich non-terrestrial cell provides the signal of greatest magnitude,and is therefore the candidate for handoff. The call connection isidentified as a non-terrestrial call and is therefore managed by mobiletelecommunication switching office MT1 as disjunct from the ground-basedcalls and the handoff to non-terrestrial cell C is managed in well knownfashion. In particular, the call connection is switched from mobiletelecommunication switching office MT1 to mobile telecommunicationswitching office MT2 concurrent with the radio frequency handoff betweenthe adjacent non-terrestrial cells B and C and the link to the publicswitched telephone network PSTN is maintained via trunk T so that thereis no interruption in the call connection. Thus, aircraft AC switchesthe frequency pair for communication with the non-terrestrial cell Csimultaneously with the ground-based link being switched to acommunication path comprising link LKC to mobile telecommunicationswitching office MT2, trunk T, mobile telecommunication switching officeMT1, and trunk PT to the public switched telecommunication network PSTN.

Non-Terrestrial Cell Configuration

The non-terrestrial cell typically shares a locus with a ground-basedcell for efficiency purposes and produces an antenna pattern that isjuxtaposed to the ground-based cell site antenna pattern and relativelynon-overlapping so that transmissions are directed to non-terrestrialmobile subscriber stations rather than including ground-based mobilesubscriber stations in the antenna pattern. The non-terrestrial cellscan optionally each have a unique HLR and SID designation to distinguishthem from the ground-based cells and to enable them to be managed incall origination, establishment and handoff functions.

The non-terrestrial cell site antenna pattern can encompass a singlecell element or multiple cell elements, depending on the implementationof the various antenna elements and several variations of the antennapattern are disclosed herein. A simple single cell site pattern cancomprise a substantially cylindrical or paraboloid pattern which extendsradially out from the antenna in all directions above a planesubstantially coplanar to the Earth's surface and at an elevationcorresponding to the antenna mounting on the mast. This antenna patternencompasses all of the volume of space located within line of sight ofthe antenna site, as is shown in FIG. 3. Alternatively, the antennapattern can be divided into a plurality of segments for use as subcellsor independent cells within the area noted above. In particular, it maybe beneficial to bifurcate the cylindrical area into two segments alonga vertically oriented plane which is aligned with a diameter of thecircle which comprises the bottom base of the cell, as shown in FIG. 7.This antenna pattern enables the non-terrestrial cellular mobiletelecommunication system to manage communications in one half of thecell independent of the other half of the cell. This pattern alsoenables the antenna characteristics to be optimized for the respectivedirections of transmission which may provide efficiency in obtaining amore uniform antenna pattern for each of the two smaller regions ofcoverage. Another possible pattern of coverage for the non-terrestrialantennas is illustrated in FIG. 8 with the creation of a substantiallytoroidal antenna pattern with a second pattern occupying a central holein the toroid and extending upward in a substantially conical manner.These two antenna patterns can be managed as a single cell or cancomprise two separate and independent cells. Alternatively, the toroidalsection can be divided into two or more segments and managed as separatecell elements. Thus, it is evident from this description, that thenon-terrestrial cells have greater flexibility of implementation thanthe ground-based cells and comprise at least one cell within apredetermined three-dimensional volume of space. Thus, the controlsoftware can implement a soft handoff within a single cell, and a hardhandoff between adjacent non-terrestrial cells. The hard handoffs switchfrequencies while the soft handoffs do not, and in the hard handoff, itis determined by the mobile telephone switching office while the softhandoff is determined by the transmitter controller.

Multidimensional Cellular Antenna Characteristics

The antenna located on a ground-based mobile subscriber station, such asan automobile, truck or boat, is vertically polarized and the antennalocated on the ground-based station is likewise vertically polarized toprovide more efficient coupling between the antennas. A differentpolarization between these antennas would have a marked effect on theeffectiveness of the transmissions between the antennas. Theground-based antenna is mounted as high as practical since the coverageis a function of antenna elevation. The non-terrestrial antenna pointsskyward and therefore mounting height is far less relevant. Thenon-terrestrial antenna can be mounted below the ground-based antenna asshown in FIG. 2 or above the ground-based antenna. Non-terrestrialsubscriber stations, such as aircraft, receive noise signals fromground-based sources, while in the reverse signal direction, thenon-terrestrial cell site receiver does not receive signals from manynoise sources since the only active sources of radio signals in thenon-terrestrial region are the non-terrestrial subscriber stations. Asnoted above, the polarization of the non-terrestrial antenna elementsshould be substantially orthogonal to the polarization of theground-based antenna elements. Therefore, the non-terrestrial antennaelements are horizontally polarized. The tower on which the antennaelements are mounted is largely transparent to the horizontallypolarized non-terrestrial antenna radio frequency transmissions sincethe polarization of the signals is horizontal in nature and the tower isvertically oriented. In addition, the tower braces are diagonal in theirorientation and therefore do not represent a substantial source ofinterference. The preferred implementation of the non-terrestrialantenna elements is shown in FIG. 9 and comprise a slotted waveguideantenna element with an optional associated zenithally oriented antennaelement for both the receive antenna elements as well as the transmitantenna elements. The slotted waveguide antenna element produces thetoroidal pattern illustrated in FIG. 8, while the zenithally orientedantenna element produces the substantially cylindrical pattern locatedin the hole in the torus. The zenithally oriented antenna element can beany of a number of typical antenna elements, including, but not limitedto: dipole, folded dipole, helix, Yagi and the like. The helix antennaprovides a benefit in that the antenna pattern produced by such anelement is circularly polarized and therefore is relatively insensitiveto the direction of movement of the non-terrestrial subscriber stationas the non-terrestrial subscriber station traverses the area near to andabove the antenna. In the implementation illustrated in FIG. 9, for thecellular radio frequencies, the slotted waveguide antenna element ispreferably mounted on to the existing antenna tower which is used tosupport the antenna for ground-based cells. As shown in FIG. 9, theantenna elements are mounted a sufficient distance D from the tower toreduce interference.

A slotted waveguide antenna consists of a length L of waveguide that isconstructed to implement a multi-element antenna which produces afocused receive pattern. Typically, the receive pattern of the slottedwaveguide antenna is formed to receive signals from only a segment ofspace (controlled field of view), with the precise receive pattern beingcreated by management of the size, location and geometry of the slotscut into the waveguide. A slot cut into the waveguide wall is connectedto the conductors of a twin line feed, placed in the interior of theslotted waveguide. The waveguide slots emit power received from the twinline feed into free space. The spacing and/or orientation of the slotsalong the edge of the waveguide are used in order to control apertureillumination. The slotted waveguide antenna can be mechanically tiltedor the produced antenna pattern electrically steered to provide apredetermined amount of uptilt to the antenna pattern, which uptiltreduces the production of multi-path interference signals as describedbelow.

In the embodiment disclosed herein, the shaped beam pattern encompassesthe volume of space located above and radially around the antennaelements which are mounted on the antenna tower. The antenna cancomprise either a single, or multiple antenna elements, which aredesigned to produce a receive characteristic pattern which providessubstantially uniform coverage for the entire non-terrestrial cell. Inparticular, the antenna pattern covers the region of space above anantenna horizon, which antenna horizon extends radially from the antennamast to the physical horizon, and at the elevation which substantiallycorresponds to the antenna element mounting height on the antenna tower.As a practical implementation, the antenna is mounted with a slight(typically 4°) uptilt to minimize the production of multi-path signals.The antenna criteria are also: a horizontally polarized beam to matchthe non-terrestrial subscriber station transmitter signal polarization,and a beam pattern which exhibits a sharp reduction in gain forelevation angles below the antenna horizon.

The reduction of the ground reflections of signals is important due tothe multi-path phenomena. Multi-path is illustrated in FIG. 11 whereinthe signals produced by a transmitting source reach the receiver overmany different paths, including direct reception of the generatedsignals and multi-path reception of the generated signals due toreflections from the ground surface. When the path length of the varioussignal paths are integral wavelength multiples of the fundamentalwavelength, this causes nulls which repeat in a fixed pattern, therebycausing reduction in signal power at these points. The antenna uptiltused in the non-terrestrial antenna reduces these nulls by reducing theenergy illumination of the ground.

Non-Terrestrial Mobile Subscriber Stations

In the above description of the multidimensional cellular communicationsystem, the non-terrestrial mobile subscriber stations are assumed forthe purpose of the description to be a small fixed wing aircraft.However, the nature of the mobile unit in which the mobile subscriberstation is installed is not limited to this application. In particular,the mobile unit can be a lighter than air craft, a helicopter, or acommercial multipassenger fixed wing aircraft, or the like. The onlylimiting factor is that the mobile unit is operational in thenon-terrestrial cells rather than the ground-based cells when acommunication connection is established. A specific exception to thisgeneral rule is that a non-terrestrial cell can be established at, forexample, an airport location to serve the aircraft located on the groundprior to the aircraft taking off and entering the non-terrestrial cellextant in the region of space above the airport. This "ground-based"non-terrestrial cell can operate on a low power basis, since thetransmit range can be limited to the bounds of the airport, therebyavoiding interference with the adjacent non-terrestrial cells.

The mobile unit is typically equipped with an electronics unit whichincludes the transmitter, receiver and control circuits well known incellular communications. The apparatus also includes an antenna, whichis typically mounted on the exterior surface of the mobile unit. Theantenna mounting can be directly fixed to the mobile unit or can belocated in a separate unit which is mounted on the exterior surface ofthe mobile unit. In this latter case, the antenna can be mechanicallysteered so that the radiation pattern of the antenna elements can bealigned with the cell site transmitter and receiver antennas to therebyenhance the quality of the communication therebetween. Alternatively,the antenna can be electronically steered by adjusting the phase and/ormagnitude of the signals applied to the antenna elements of an array asis well known in this technology. The power output of thenon-terrestrial transmitters can also be regulated as a function of thedistance from the cell site transmitter antenna to ensure a relativelyconstant signal level.

Furthermore, the transmitter, receiver and control circuits may be usedto serve a single handset unit or can be multiplexed to serve aplurality of handset units as in a commercial airliner application. Thehandsets can be hard wired to the electronics unit or can be wirelessunits of limited communication range which interconnect with theelectronics unit via radio frequency transmissions. In the multi-userapplication, the electronics unit can comprise a "mini-cell" wherein thevarious handsets are managed by the electronics unit in a manneranalogous to that performed by the typical cell site/MTSO. Thus, thehandset units can be of a different technology than the single handsetapplications, with the electronic unit performing an integrationfunction as well as the multiplexing function. The handsets can bepersonal communication system (PCS) units, pagers, code divisionmultiple access (CDMA) units, or any other wireless communicationdevices which are in use by individuals. The electronics unit receivesthe signals generated by the various handset units and formats (ifnecessary) the data contained in these transmissions into the formatused for the radio link transmissions to the cell site. The resultantsignal is applied via the transmitter contained in the electronics unitto the antenna mounted on the exterior of the mobile unit, whichradiates the signals to the serving cell site. The communications in thereverse direction are managed in a complementary manner as is wellknown. The handset units each have a unique identification which enablesthe underlying cellular communication network to communicate with theunit. The electronics unit can therefore perform the handsetregistration function by polling the handset units extant in the spaceserved by the electronics unit to thereby identify these units. Thisunit identification data can then be transmitted to the cell site viathe control channels to enable the cellular network to ascertain thelocation of these particular units. Thus, when a ground-based subscriber(for example) initiates a call to one of these handset units, the MSTOcan scan the mobile subscriber records to locate the identified mobilesubscriber station. This data is then used by the cellular network toestablish a communication link to the identified mobile subscriber unit.In this manner, what may traditionally may be considered ground-basedmobile subscriber stations can function as non-terrestrial subscriberstations in the environment just described.

Summary

The multidimensional cellular mobile telecommunications system extendsthe usage of existing cellular mobile telecommunication frequenciesallocated for ground-based communications to non-terrestrial mobilesubscriber stations by adding an overlay of non-terrestrial cells ofpredetermined geometry and locus in space to the existing ground-basedcellular cell site network. The polarization of the signals produced bythe non-terrestrial antenna elements is substantially orthogonal to thepolarization of the ground-based antenna signals to thereby minimize thepossibility of interference with the vertically polarized ground-basedsignals. Furthermore, the control signals exchanged between thenon-terrestrial mobile subscriber stations and the cell site controllerare architected to avoid the possibility of interference withground-based cell site transmitter-receiver pairs. In this manner, theexisting two dimension mobile cellular telecommunication network isextensible by use of these novel methods and apparatus to create amultidimensional cellular mobile telecommunication system which makesuse of the presently allocated frequencies and presently providedservices.

What is claimed:
 1. A telecommunication system for providing cellularradio communication with non-terrestrial mobile subscriber stationsusing radio frequencies allocated for ground-based mobiletelecommunications, comprising:at least one radio transmitter forgenerating communication signals transmitted to non-terrestrial mobilesubscriber stations at radio frequencies allocated for ground-basedmobile subscriber stations, said generated communication signalscomprising control and user data signals; at least one radio receiverfor receiving communication signals generated by said non-terrestrialmobile subscriber stations at radio frequencies allocated for saidground-based mobile subscriber stations, said received communicationsignals comprising control and user data signals; and wherein saidcommunication signals generated by said at least one radio transmitterand said non-terrestrial mobile subscriber stations comprise at leastone channel for exchanging control signals, said at least one channelbeing selected to contain control signals incapable of being used bysaid ground-based mobile subscriber stations.
 2. The telecommunicationsystem of claim 1 wherein communication signals transmitted to saidground-based mobile subscriber stations comprise a plurality ofcommunication channels, a first set of said communication channels beingused for control signals and a second set of said communication channelsbeing used for user data signals, said at least one radio transmittercomprising:means for generating communication signals, transmitted tosaid non-terrestrial mobile subscriber stations, said generatedcommunication signals comprising a plurality of communication channels;means for allocating a first set of said generated plurality ofcommunication channels for user data signals; and means for allocatingat least one of said generated plurality of communication channels assaid at least one channel for exchanging for control signals, which saidat least one channel correspond to communication channels in said firstset of said communication channels transmitted to said ground-basedmobile subscriber stations.
 3. The telecommunication system of claim 2wherein communication signals transmitted to said ground-based mobilesubscriber stations comprise radio signals of a first polarization, saidat least one radio transmitter comprising:means for generatingcommunication signals, transmitted to said non-terrestrial mobilesubscriber stations, said generated communication signals comprisingradio signals of a second polarization, said second polarization beingdifferent than said first polarization.
 4. The telecommunication systemof claim 3 wherein said means for generating produces radio signals ofsaid second polarization which is substantially orthogonal to said firstpolarization.
 5. The telecommunication system of claim 3 wherein saidradio signals of a first polarization are polarized in a verticaldirection, said means for generating produces radio signals ofhorizontal polarization.
 6. The telecommunication system of claim 1wherein communication signals transmitted to said non-terrestrial mobilesubscriber stations comprise a plurality of communication channels, afirst set of said communication channels being used for control signalsand a second set of said communication channels being used for user datasignals, said telecommunication system further comprising:means forgenerating communication signals, transmitted to said ground-basedmobile subscriber stations, comprising a plurality of communicationchannels; means for allocating a first set of said generated pluralityof communication channels for user data signals; and means forallocating at least one of said generated plurality of communicationchannels for control signals, which said at least one channel correspondto communication channels in said first set of said communicationchannels transmitted to said non-terrestrial mobile subscriber stations.7. The telecommunication system of claim 1 wherein said at least oneradio transmitter comprises:means for generating communication signalswhich comprise a plurality of communication channels; means forallocating a first set of said generated plurality of communicationchannels for user data signals; and means for allocating at least one ofsaid generated plurality of communication channels for control signals.8. The telecommunications system of claim 7 wherein communicationsignals transmitted to said ground-based mobile subscriber stationscomprise radio signals of a first polarization, said at least one radiotransmitter further comprises:means for transmitting said generatedcommunication signals as radio signals of a second polarization whichsecond polarization is substantially orthogonal to said firstpolarization.
 9. A method of operating a telecommunication system forproviding cellular radio communication with non-terrestrial mobilesubscriber stations using radio frequencies allocated for ground-basedmobile telecommunications, said method comprising the steps of:operatingat least one radio transmitter to generate communication signalstransmitted to non-terrestrial mobile subscriber stations at radiofrequencies allocated for ground-based mobile subscriber stations, saidgenerated communication signals comprising control and user datasignals; operating at least one radio receiver to receive communicationsignals generated by said non-terrestrial mobile subscriber stations atradio frequencies allocated for said ground-based mobile subscriberstations, said received communication signals comprising control anduser data signals; and implementing said communication signals generatedby said at least one radio transmitter and said non-terrestrial mobilesubscriber stations to comprise at least one channel for exchangingcontrol signals, said at least one channel being selected to containcontrol signals incapable of being used by said ground-based mobilesubscriber stations.
 10. The method of operating a telecommunicationsystem of claim 9 wherein communication signals transmitted to saidground-based mobile subscriber stations comprise a plurality ofcommunication channels, a first set of said communication channels beingused for control signals and a second set of said communication channelsbeing used for user data signals, said method of operating said at leastone radio transmitter comprising:generating communication signals,transmitted to said non-terrestrial mobile subscriber stations, saidgenerated communication signals comprising a plurality of communicationchannels; allocating a first set of said generated plurality ofcommunication channels for user data signals; and allocating at leastone of said generated plurality of communication channels as said atleast one channel for exchanging for control signals, which said atleast one channel correspond to communication channels in said first setof said communication channels transmitted to said ground-based mobilesubscriber stations.
 11. The method of operating a telecommunicationsystem of claim 10 wherein communication signals transmitted to saidground-based mobile subscriber stations comprise radio signals of afirst polarization, said method of operating said at least one radiotransmitter comprising:generating communication signals, transmitted tosaid non-terrestrial mobile subscriber stations, said generatedcommunication signals comprising radio signals of a second polarization,said second polarization being different than said first polarization.12. The method of operating a telecommunication system of claim 11wherein said step of generating produces radio signals of said secondpolarization which is substantially orthogonal to said firstpolarization.
 13. The method of operating a telecommunication system ofclaim 11 wherein said radio signals of a first polarization arepolarized in a vertical direction, said means for generating producesradio signals of horizontal polarization.
 14. The method of operating atelecommunication system of claim 9 wherein communication signalstransmitted to said non-terrestrial mobile subscriber stations comprisea plurality of communication channels, a first set of said communicationchannels being used for control signals and a second set of saidcommunication channels being used for user data signals, said method ofoperating said telecommunication system further comprising:generatingcommunication signals, transmitted to said ground-based mobilesubscriber stations, comprising a plurality of communication channels;allocating a first set of said generated plurality of communicationchannels for user data signals; and allocating at least one of saidgenerated plurality of communication channels for control signals, whichsaid at least one channel correspond to communication channels in saidfirst set of said communication channels transmitted to saidnon-terrestrial mobile subscriber stations.
 15. The method of operatinga telecommunication system of claim 9 wherein said method of operatingsaid at least one radio transmitter comprises:generating communicationsignals which comprise a plurality of communication channels; allocatinga first set of said generated plurality of communication channels foruser data signals; and allocating at least one of said generatedplurality of communication channels for control signals.
 16. The methodof operating a telecommunications system of claim 15 whereincommunication signals transmitted to said ground-based mobile subscriberstations comprise radio signals of a first polarization, said method ofoperating said at least one radio transmitter furthercomprises:transmitting said generated communication signals as radiosignals of a second polarization which second polarization issubstantially orthogonal to said first polarization.
 17. Atelecommunication system for concurrently providing cellular radiocommunication to a first set of mobile subscriber stations and a secondset of mobile subscriber stations at the same radio frequencies, absentradio communication from said first set of mobile subscriber stationsinterfering with radio communication from said second set of mobilesubscriber stations while cellular radio communication is concurrentlypresent on identical ones of said radio frequencies, comprising:a firstradio transmitter for generating communication signals transmitted tomobile subscriber stations in said first set of mobile subscriberstations at radio frequencies allocated for mobile subscriber stationsin said second set, said generated communication signals comprisingcontrol and user data signals; a first radio receiver for receivingcommunication signals generated by mobile subscriber stations in saidfirst set of mobile subscriber stations at radio frequencies allocatedfor mobile subscriber stations in said second set of mobile subscriberstations, said received communication signals comprising control anduser data signals wherein said first radio transmitter generates andsaid first radio receiver receives said communication signals for saidfirst set of mobile subscriber stations at a polarization which issubstantially orthogonal to a polarization of communication signals forsaid second set of mobile subscriber stations; and wherein said controlsignals generated by said first radio transmitter and said mobilesubscriber stations in said first set of mobile subscriber stationscomprise at least one channel for exchanging control signalstherebetween, which control signals are incapable of being used by saidmobile subscriber stations in said second set of mobile subscriberstations.
 18. The telecommunication system of claim 17 wherein saidcommunication signals for said first set of mobile subscriber stationsare polarized in a vertical direction and said communication signals forsaid second set of mobile subscriber stations are polarized in ahorizontal polarization.
 19. The telecommunication system of claim 17further comprising:a second radio transmitter for generatingcommunication signals transmitted to said mobile subscriber stations insaid second set of mobile subscriber stations at said allocated radiofrequencies, said generated communication signals comprising control anduser data signals; a second radio receiver for receiving communicationsignals generated by said mobile subscriber stations in said second setof mobile subscriber stations at said allocated radio frequencies, saidreceived communication signals comprising control and user data signals;and wherein said control signals generated by said second radiotransmitter and said mobile subscriber stations in said second set ofmobile subscriber stations comprise at least one channel for exchangingcontrol data therebetween which is incapable of being used by saidmobile subscriber stations in said first set of mobile subscriberstations.
 20. The telecommunication system of claim 17 wherein saidfirst radio transmitter comprises:means for generating communicationsignals which comprise a plurality of communication channels; means forallocating a first set of said generated plurality of communicationchannels for user data signals; and means for allocating at least one ofsaid generated plurality of communication channels for control signals.21. The telecommunications system of claim 19 wherein said second radiotransmitter generates and said second radio receiver receives saidcommunication signals for said second set of mobile subscriber stationsat a polarization which is substantially orthogonal to a polarization ofcommunication signals for said first set of mobile subscriber stations.22. A method of operating a telecommunication system for providingcellular radio communication to a first set of mobile subscriberstations and a second set of mobile subscriber stations at the sameradio frequencies, absent radio communication from said first set ofmobile subscriber stations interfering with radio communication fromsaid second set of mobile subscriber stations while cellular radiocommunication is concurrently present on identical ones of said radiofrequencies, said method comprising the steps of:operating a first radiotransmitter for generating communication signals transmitted to mobilesubscriber stations in said first set of mobile subscriber stations atradio frequencies allocated for mobile subscriber stations in saidsecond set, said generated communication signals comprising control anduser data signals; operating a first radio receiver for receivingcommunication signals generated by mobile subscriber stations in saidfirst set of mobile subscriber stations at radio frequencies allocatedfor mobile subscriber stations in said second set of mobile subscriberstations, said received communication signals comprising control anduser data signals; wherein said first radio transmitter generates andsaid first radio receiver receives said communication signals for saidfirst set of mobile subscriber stations at a polarization which issubstantially orthogonal to a polarization of communication signals forsaid second set of mobile subscriber stations; and implementing saidcontrol signals generated by said first radio transmitter and saidmobile subscriber stations in said first set of mobile subscriberstations to comprise at least one channel for exchanging control signalstherebetween, which control signals are incapable of being used by saidmobile subscriber stations in said second set of mobile subscriberstations.
 23. The method of operating said telecommunication system ofclaim 22 wherein said communication signals for said first set of mobilesubscriber stations are polarized in a vertical direction and saidcommunication signals for said second set of mobile subscriber stationsare polarized in a horizontal polarization.
 24. The method of operatingsaid telecommunication system of claim 22 further comprising:operating asecond radio transmitter for generating communication signalstransmitted to said mobile subscriber stations in said second set ofmobile subscriber stations at said allocated radio frequencies, saidgenerated communication signals comprising control and user datasignals; operating a second radio receiver for receiving communicationsignals generated by said mobile subscriber stations in said second setof mobile subscriber stations at said allocated radio frequencies, saidreceived communication signals comprising control and user data signals;and implementing said control signals generated by said second radiotransmitter and said mobile subscriber stations in said second set ofmobile subscriber stations to comprise at least one channel forexchanging control data therebetween which is incapable of being used bysaid mobile subscriber stations in said first set of mobile subscriberstations.
 25. The method of operating said telecommunication system ofclaim 22 wherein said method of operating said first radio transmittercomprises:means for generating communication signals which comprise aplurality of communication channels; means for allocating a first set ofsaid generated plurality of communication channels for user datasignals; and means for allocating at least one of said generatedplurality of communication channels for control signals.
 26. The methodof operating said telecommunications system of claim 25 wherein saidmethod of operating said second radio transmitter generates and saidmethod of operating said second radio receiver receives saidcommunication signals for said second set of mobile subscriber stationsat a polarization which is substantially orthogonal to a polarization ofcommunication signals for said first set of mobile subscriber stations.